Fuel for engines

ABSTRACT

Nitroparaffins are added to gasoline together with synthetic lubricants of the ester type (e.g. synthetic jet turbine oil) and are used as fuel in glow engines, jet engines and internal combustion engines in general to improve combustion efficiency, especially by lowering fuel consumption while increasing the output and providing cleaner burning.

United States Patent 11 1 Michaels Aug. 19, 1975 FUEL FOR ENGINES [76] Inventor: James Michaels, 26 Valmont Ln.,

Commack, NY. H725 [22] Filed: Sept. 29, 1972 [2]] Appl. No: 293,576

Related US. Application Data [63] Continuation-impart of Ser, No. 150.822. June 7,

[97 l abandoned [52] U.S. Cl. 44/57; 44/58; 44/72;

252/56 R [5 l] Int. Cl ..C10l 1/22 [58] Field of Search 44/57, 58, 72; 252/56 R [56] References Cited UNITED STATES PATENTS 2491968 2/l950 Young et al. 252/56 R 2,499,984 3/[950 Beavers et al 252/56 R 2,584,803 2/1952 Hannum 1 44 72 2,590,451 3 1952 Perry v 1 1 252/56 R 2,611,744 9/1952 Kipp 252/56 R 2,618,602 11 1952 Bartlett 252 56 R 2,673,793 3 1954 Brodhacker 44 53 Primary ExamillerAllen B. Curtis Assistant Examiner-Y. H. Smith ABSTRACT l6 Claims, N0 Drawings 1 FUEL FOR ENGINES CROSS'REFERENCE TO RELATED APPLICATION This application is a. continuation-in-part of my copending US. application Ser. No. 150,822 filed June 7, 1971, now abandoned.

BACKGROUND OF THE INVENTION Nitroparaffins, such as monoand di-nitroderivatives of alkanes having from 1 to 4 carbon atoms, have been proposed for use as fuels to increase engine power in internal combustion engines without attendant penalty of increased engine size or mechanical complexity. Being thermally sensitive, they unfortunately exhibit a tendency to induce pre-ignition when used in internal combustion engines of the reciprocating type. To reduce that tendency, such nitroparaffins are commonly blended with lower alcohols, such as methanol. Previous attempts to blend significant proportions of nitroparaffins into gasoline type engine fuels have failed because these nitroparaffins are not readily miscible in hydrocarbons. For example, nitromethane is only slightly soluble in gasoline, to the extent of no more than about 5 percent. Solubility of nitroparaffins in gasoline can be increased by addition of substantial proportions of aromatic hydrocarbons, such as benzene. This is an expensive expedient and even then the proportions of nitroparaffins which can be incorporated are limited.

The present invention relates to fuels for engines, reciprocating piston engines as well as turbine engines. The invention, in one particular aspect, is concerned with fuel for glow engines used for model aircraft.

It is an object of the present invention to provide fuel for use in internal combustion engines which is better than fuels which are now in use, namely, which provide lower fuel consumption, higher horsepower output and cleaner burning.

Other objects will become apparent from the following description.

SUMMARY OF THE INVENTION In accordance with the present invention, it was found that improved fuels for internal combustion engines, viz. reciprocating piston engines, rotary piston engines as well as turbine engines, providing improved combustion efficiency, resulting in lower fuel consumption, increased horsepower output and cleaner burning, are obtained by blending regular petroleum ether, namely gasoline, with certain nitroparaffins, namely nitroalkanes having one or two nitro groups and containing up to four carbon atoms, such as nitromethane, nitroethane, l-nitropropane, and the like. In accordance with the present invention it was further discovered that these nitroparaifins can be rendered miscible in gasoline by including in the nitroparaffin/gasoline blend a synthetic ester lubricating oil.

Thus, in accordance with the present invention there are provided fuel compositions for internal combustion engines comprising a homogeneous blend of A. 5 to 95 parts by volume of gasoline, and correspondingly B. 95 to 5 parts by volume of a blend comprising a. to 90 parts by volume of a nitroalkane having one or two nitro groups, and containing up to four carbon atoms, and mixtures thereof, and correspondingly b. to I0 parts by volume of a normally liquid ester lubricant having a viscosity at F of at least 1 cSt. selected from the group consisting of esters of i. linear primary alcohols and linear dicarboxylic acids,

ii. branched chain primary alcohols and linear dicarboxylic acids,

iii. branched chain monocarboxylic acids and lin ear dihydric alcohols and/or polyalkylene glycols,

iv. linear primary alcohols and branched chain dicarboxylic acids,

v. neopentyl polyols and monocarboxylic acids,

straight chain or branched, and

vi. mixed complex esters of primary alcohols,

straight chain or branched, monoand dicarboxylic acids, straight chain or branched, and polyalkylene glycols,

and mixtures thereof, with the proviso that the proportion of ester lubricant in the fuel composition may not exceed 25 percent by volume.

It was unexpected and surprising that addition of even minor proportions of above-described ester lubricant would render perfectly miscible otherwise immiscible nitroalkane/gasoline blends, because neither mineral oil based lubricants nor naturally occurring ester oils, such as castor oil or cottonseed oil are capable of providing such miscibility. Inclusion of ester lubricant in fuel compositions for reciprocating combustion engines has the further advantage of providing internal lubrication within the engine, thereby reducing engine wear and improving engine efficiency. When used in two-cycle engines, particularly air cooled engines, which do not carry their own oil supply as four cycle engines do, the ester lubricant can serve as the normally required lubricant additive, although a separate supply of lubricating oil may be added to the fuel, if desired.

DETAILED DESCRIPTION OF THE INVENTION The gasoline component of the present fuel compositions are volatile hydrocarbons having boiling range in the order of to 400F. Any commercially available type of gasoline is suitable. Usually, such gasolines contain straight chain, branched and cyclic hydrocarbons, in varying proportions, of about 5 to 12 carbon atoms, which may optionally contain minor proportions of aromatic hydrocarbons. They may include natural gasolines, also known as casinghead gasoline, as well as gasoline obtained by cracking of higher boiling hydrocarbons, or by hydrocracking, reformation and alkylation. These gasolines may optionally contain added antiknock compounds, such as tetraethyl lead, as well as deposit modifiers, antioxidants, metal deactivators, corrosion inhibitors, anti-icing agents, detergents, upper-cylinder lubricants and dyes, such as are usually added to commercial grades of gasoline. However, the straight, unblended hydrocarbons having from about 5 to about 12 carbon atoms, linear as well as branched chain and cyclic, such as n-hexane, n'heptane, noctane, iso-octane, the various nonanes, decanes and the like are equally suited for use in the present fuel compositions and are intended to be included in the term gasoline.

Preferred nitroalkanes are the normally liquid nitroalkanes of one to four carbon atoms having one or two nitro groups. They are commercially available. Specific examples of preferred nitroalkanes include nitro methane nitroethane, l-nitropropane 2- nitropropane, Z-nitrobutane as well as 2,2- dinitropropane, although the latter is a solid at normal temperature and pressure. Of these, nitroethane, l nitropropane, 2-nitropropane and especially nitromethane are most preferred.

Ester lubricants of the type suitable for use in the fuel compositions of the present invention include those which have found wide use as synthetic oil in modern jet engines. These include the commercially available synthetic lubricating oils metting Military Specifications MlL-L-7808 and MIL'L9236 of the ester type. Specific examples of commercially available synthetic oils suitable for use in the compositions of the present invention include Texaco SATO No. 7730 Synthetic Aircraft Turbine Oil, Monsanto Skylube No. 450 Jet Engine Oil, and Mobile [I Turbine Oil.

Ester lubricants of dicarboxylic acids, straight chain or branched, and primary alcohols, straight chain or branched, generally have the formula wherein a. n is an integer of from 2 to l0, preferably from 4 to 8; b. R, and R,, which may be the same or different, are alkyl, straight chain or branched, having from 4 to 12 carbon atoms, preferably 6 to carbon atoms. Preferably, when in formula (1), above, C H has a straight chain, then R, and R are branched, and when C l-1 is branched, then R, and R are straight chain. Straight chain R, and R groups are preferred.

Ester lubricants based on dihydric alcohols and/or polyalkylene glycols generally have the formula RICOO yri ent wherein a. m is an integer of 2 to l2, preferably 2 to 8, most preferably 2; b. r is an integer of 1 to 10, preferably 1 to 6, most preferably 1; and c. R, and R have the same meanings as described above in connection with their use in formula (I); provided that when r is greater than 1, then m is preferably 2 or 3.

Ester lubricants of neopentyl polyols and monocarboxylic acids generally have the formula e -T a (Ill) wherein R to R which may be the same or different, are selected from the group consisting of a. alkyl, straight chain or branched, having from 1 to 10 carbon atoms, preferably from I to 2 carbon atoms, and

b. radicals of the formula C,,H ,OOCR-,

wherein 5 i. s is an integer of from I to 4, preferably l, and ii. R, has the same meaning as R, and R described above in connection with formula (l), provided that not more than two of the R to R groups may be alkyl groups.

Mixed complex esters of primary alcohols, straight chain or branched, monoand di-carboxylic acids, straight chain or branched, and polyalkylene glycols include those having the formulas R, OOC C,,H COO l- (C H O) OC C ll, COO] R,

prim. dicarb. polyalkylene dicarb. prim. alcohol acid glycol acid alcohol and A 1 m 2m )r n 2n m 2m )r OCR,

monocarb. polyalk. dicarb. polyalk. monocarb. acid glycol acid glycol acid in above formulas (IV) and (V) R,, R m, n and r have the meanings discussed above in connection with formulas (l) and (ll), and x and y are integers of from 1 to 4, preferably 1 or 2.

It is to be understood that the above described ester oils may be used in the fuel compositions of my invention in the form of discrete, individual compounds, or as mixtures of isomers, homologes or different compounds. Commercially available ester oils of the above description usually contain additives to improve their performance as lubricants, which additives do not ordinarily adversely affect performance of such oils in my fuel compositions. ln general, for reasons of ready availability, use of ester oil in the form of commercially available synthetic ester turbine oils is preferred.

Preferred ester oils, principally for reasons of availability, are those having formula (1), above, derived from dicarboxylic acids. Specific examples of preferred dicarboxylic acids for making ester oils of formula (I) include adipic acid, azelaic acid, and sebacic acid. Specific examples of preferred alcohols for esterification with such acids to make preferred ester oils of formula (I) include straight and, more preferably, branched chain alcohols of 8 to 10 carbon atoms, such as di(2- ethylhexyl) alcohol, oxo-alcohols of 8 to l0 carbon atoms, which are mixtures of isomers and homologes, and 3,5,5-trimethyl hexyl alcohol. Thus, specific examples of preferred ester oils include the adipates, sebacates and azelates of 2-ethylhexyl alcohol, of C to C m oxo-alcohols, and of 3,5,5-trimethylhexyl alcohol.

A further specific example of a preferred ester oil ac cording to formula (I), above, is the dipelargonate of dipropylene glycol.

Ester oils suitable for use in the fuel compositions of the present invention must be normally liquid and must have a viscosity of at leat l cSt. ut l()()F. This minimum viscosity requirement serves as a convenient, practical way of specifying a minimum molecular weight, and thus, carbon atom content requirement for such oils. This designation was chosen in preference over other methods because of its simplicity, because analysis of such oils, especially if in the form of mix tures, is very difficult. Generally, viscosity of these ester oils increases with increasing carbon atom content, i.e. with increasing molecular weight. For example, the sebacinate, azelate and adipate of 2 ethylhexyl alcohol respectively have viscosities of about 12.5, ll.l and 8.2 cSt. at lOF, and of 3.3, 3.0 and 2.4 cSt. respectively at 230F. Their flashpoints are in the order of 200 to 220C. While the viscosity limitation is intended as a limitation on lower carbon content, the requirement that these ester oils are normally liquid" furnishes a limitation on upper level of carbon content, since with increasing carbon contents these esters change from normally liquid oils to greases and waxes.

These ester oils are made by usual procedures involv ing esterification of the required acid and alcohol in the presence of acidic catalyst, such as sodium hydrogen sulfate, phosphoric acid and its salts, trialkyl or triaryl phosphates, ptoluene sulfonic acid, or mineral acids, under removal of water formed in the reaction by distillation, preferably in the form of its azeotropes with benzene or toluene. Asymmetrical esters and complex esters, of course, require double or multiple step esterification.

For a more complete description of ester oils suitable for use in the fuel compositions of the present invention reference is made to Ullmans Encyclopaedie der Technischen Chemie, 3rd. Ed., Urban & Schwarzenberg, Muenchen Berlin (1964), Vol. 15, p. 285 et seq., and references cited therein.

The fuel compositions of the present invention may contain from 5 to 95 percent by volume of gasoline, and from 0.5 to 85.5 percent by volume of nitroalkane. Preferred fuel compositions contain from about 20 to 80 percent by volume, or, more preferably yet, 40 to 80 percent by volume of gasoline, and about to 65 percent, more preferably [5 to 45 percent by volume of nitroalkane.

The ester oil is preferably employed in minimum amount required to provide a homogeneous liquid fuel compositions. Use of less than that amount results in non homogeneous compositions, with concomitant physical separation of liquid components into layers, and use of excess amounts of ester oil is wasteful and may result in excess carbon deposition within the engine, fouling of sparkplugs and generally unsatisfactory engine operation. No general rule can be set down fixing precise amounts of ester oil required to achieve ho mogeneity of the compositions, since that amount depends on variables such as the type of gasoline, nitroalkane and ester oil, as well as the proportions in which gasoline and nitroalkane are incorporated into the composition. However, the required amounts of ester oil are readily determined by simple experimentation of routine nature, e.g. by first adding the nitroalkane to the gasoline in desired amount, then adding the ester oil in small portions, followed by thorough mixing after each addition, until a homogeneous blend is obtained. As a general guide, use of ester oil in proportions of from 1 to 4 parts of ester oil to 8 parts of nitroalkane will ordinarily provide a homogeneous blend.

It has further been found that it is sometimes advantageous to add small amounts of propylene oxide, C;,H,,(), to the fuel compositions of the present invention, to obtain further improvement in engine operation.

Also, it is often desirable to use blends of various nitroalkanes. For example, a blend of 3 parts of nitromethane, 1 part nitroethane, 2 parts nitropropane and /2 part propylene oxide was found to be most efficient. Other possible blend compositions may be as follows: 4 parts nitroethane and l part nitromethane, 4 parts ni tromethane, 3 parts propylene oxide and 1 part nitroethane; 2 parts nitromethane, 1 part nitroethane and 1 part nitropropane; 1 part nitroethane and 1 part nitropropane; l part nitromethane, 1 part nitroethane and 1 part nitropropane.

A specific example of a preferred fuel composition for use in glow plug engines comprises: about parts by volume of gasoline,

16 parts by volume of nitromethane, and

4 parts by volume of ester lubricant (e.g. Mobile II Turbine Oil, sold by Mobil Oil Co.)

The fuel mixture can be used in glow engines which will then perform on par with or better than alcohol base fuels containing nitroalkane, such as nitromethane. The advantages of using the fuel of the present invention are found in lower fuel consumption due to high BTU of energy developed resulting in higher horsepower output and cleaner burning, since the added blends (of nitroalkane and their mixtures) improve combustion efficiency. The same advantages occur when this fuel is used in other internal combustion engines or jet engines.

Since various changes and modifications may be made in the invention without departing from the spirit or essential characteristics thereof, it is intended that all matter contained in the above description shall be interpreted as illustrative only, the invention being limited only by the scope of the appended claims.

I claim:

1. Fuel composition for internal combustion engines comprising a homogeneous blend of A. 5 to volume percent of gasoline, and cone spondingly B. 95 to 5 volume percent of a blend comprising a. ID to 90 volume percent of a nitroalkane having one or two nitro groups, and containing up to four carbon atoms, and mixtures thereof, and correspondingly b. 90 to l() volume percent of a normally liquid ester lubricant having a viscosity at F. of at least l cSt. selected from the group consisting of esters of i. primary alcohols, linear or branched chain, and

dicarboxylic acids, linear or branched chain, having the formula wherein n is an integer of from 2 to 10 and R and R which may be the same or different, are alkyl, straight chain or branched, having from 4 to 12 carbon atoms,

ii. monocarboxylic acids and dihydric alcohols and/or polyalkylene glycols having the formula wherein m is an integer of from 2 to 12, r is an integer of from 1 to l0, and R and R have the afore-stated meanings,

iii. neopentyl polyols and monocarboxylic acids, straight chain or branched, having the formula wherein R to R which may be the same or different, are selected from the group consisting of l alkyl, straight chain or branched, having from 1 to 10 carbon atoms, and (2) radicals of the formula C,H ,OOCR wherein s is an integer of from 1 to 4, and R is alkyl, straight chain or branched, having from 4 to 12 carbon atoms, with the proviso that not more than two of the R to R groups may be alkyl, and

iv. mixed complex esters of primary alcohols, straight chain or branched, monoand dicarboxylic acids, straight chain or branched, and polyalkylene glycols, having the formulas and wherein R,, R,, m, n, and r have the afore-stated meanings and x and y are integers of from 1 to and mixtures thereof, with the proviso that the proportion of ester lubricant in the fuel 2. Fuel composition according to claim 1 containing from about to 80 percent by volume of gasoline and from about 15 to 65 percent by volume of nitroalkane. 3. Fuel composition according to claim 1 containing from about 40 to 80 percent by volume of gasoline and from about 15 to 45 percent by volume of nitroalkane. 4. Fuel composition according to claim 3 wherein the nitroalkane is nitromethane.

5. Fuel composition according to claim 1 wherein the ester lubricant has the formula R OOC C H COOR wherein a. n is an integer of from 2 to 10, and b. R and R which may be the same or different, are alkyl, straight chain or branched, having from 4 to l2 carbon atoms.

6. Fuel composition according to claim 5 containing from about 20 to 80 percent by volume of gasoline and from about l5 to percent by volume of nitroalkane.

7. Fuel composition according to claim 5 containing from about 40 to percent by volume of gasoline and from about l5 to 45 percent by volume of nitroalkane.

8. Fuel composition according to claim 7 wherein the nitroalkane is nitromethane.

9. Fuel composition according to claim 1 wherein the ester lubricant has the formula R COO (C H O),OCR

wherein a. m is an integer of 2 to 12,

b. r is an integer of l to 10, and

c. R and R which may be the same or different, are

alkyl, straight chain or branched; having from 4 to 12 carbon atoms.

10. Fuel composition according to claim 9 containing from about 20 to 80 percent by volume of gasoline and from about 15 to 65 percent by volume of nitroalkane.

11. Fuel composition according to claim 9 containing from about 40 to 80 percent by volume of gasoline and from about 15 to 45 percent by volume of nitroalkane.

12. Fuel composition according to claim 7 wherein the nitroalkane is nitromethane.

13. Fuel composition according to claim 1 containing about 80 parts by volume of gasoline, about 16 parts by volume of nitromethane, and about 4 parts by volume of ester lubricant.

14. Fuel composition according to claim 13 wherein the ester lubricant is an ester of branched chain primary alcohol and linear dicarboxylic acid.

15. The method of creating energy which comprises burning a fuel according to claim 1 in an internal combustion engine.

16. The method of creating energy which comprises burning a fuel according to claim 14 in a glow plug engine.

i I t UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 3300,39? DATED ugust 19, 1975' INVENTOR(S) JILHOS liehzzels It is certified that error appears in the abeve-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 15', delete metting and substitute therefor -r:ree'bing-- GOlTUIG 7, line Mfr (lrirst line 01" claim 1), add. --composition 111:1 not exceed. percent by volume.

Signed and Scaled this A rtes t:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner 01' Parents and Trademarks 

1. FUEL COMPOSITION FOR INTERNAL COMBUSTION ENGINES COMPRISING A HOMOGENEOUS BLEND OF A. 5 TO 95 VOLUME PERCENT OF GASOLINE, AND CORRESPONDINGLY B. 95 TO 5 VOLUME PERCENT OF A BLEND COMPRISING A. 10 TO 90 VOLUME PERCENT OF A NITROALKANE HAVING ONE OR TWO NITRO GROUPS, AND CONTAINING UP TO FOUR CARBON ATOMS, AND MIXTURES THEREOF, AND CORRESPONDINGLY B. 90 TO 10 VOLUME PERCENT OF A NORMALLY LIQUID ESTER LUBRICANT HAVING VISCOSITY AT 100*F, OF AT LEAST 1 CST. SELECTED FROM THE GROUP CONSISTING OF ESTERS OF I. PRIMARY ALCOHOLS, LINEAR OR BRANCHED CHAIN, AND DICARBOXYLIC ACIDS, LINEAR OR BRANCHED CHAIN, HAVING THE FORMULA
 2. Fuel composition according to claim 1 containing from about 20 to 80 percent by volume of gasoline and from about 15 to 65 percent by volume of nitroalkane.
 3. Fuel composition according to claim 1 containing from about 40 to 80 percent by volume of gasoline and from about 15 to 45 percent by volume of nitroalkane.
 4. Fuel composition according to claim 3 wherein the nitroalkane is nitromethane.
 5. Fuel composition according to claim 1 wherein the ester lubricant has the formula R1OOC - CnH2n - COOR2 wherein a. n is an integer of from 2 to 10, and b. R1 and R2, which may be the same or different, are alkyl, straight chain or branched, having from 4 to 12 carbon atoms.
 6. Fuel composition according to claim 5 containing from about 20 to 80 percent by volume of gasoline and from about 15 to 65 percent by volume of nitroalkane.
 7. Fuel composition according to claim 5 containing from about 40 to 80 percent by volume of gasoline and from about 15 to 45 percent by volume of nitroalkane.
 8. Fuel composition according to claim 7 wherein the nitroalkane is nitromethane.
 9. Fuel composition according to claim 1 wherein the ester lubricant has the formula R1COO (CmH2mO)rOCR2 wherein a. m is an integer of 2 to 12, b. r is an integer of 1 to 10, and c. R1 and R2, which may be the same or different, are alkyl, straight chain or branched, having from 4 to 12 carbon Atoms.
 10. Fuel composition according to claim 9 containing from about 20 to 80 percent by volume of gasoline and from about 15 to 65 percent by volume of nitroalkane.
 11. Fuel composition according to claim 9 containing from about 40 to 80 percent by volume of gasoline and from about 15 to 45 percent by volume of nitroalkane.
 12. Fuel composition according to claim 7 wherein the nitroalkane is nitromethane.
 13. Fuel composition according to claim 1 containing about 80 parts by volume of gasoline, about 16 parts by volume of nitromethane, and about 4 parts by volume of ester lubricant.
 14. Fuel composition according to claim 13 wherein the ester lubricant is an ester of branched chain primary alcohol and linear dicarboxylic acid.
 15. The method of creating energy which comprises burning a fuel according to claim 1 in an internal combustion engine.
 16. The method of creating energy which comprises burning a fuel according to claim 14 in a glow plug engine. 